How Expansive Clay Soil Affects Manassas, VA Homes

Both soil erosion and soil swelling can change the way that your soil can support your home structures. With soil erosion, water or wind washes soil levels to lower than normal, which can be very problematic for your home. For instance, when soil gets washed away underneath concrete beds, this can leave voids, or gaps, which can cause your concrete to crack or sink—given enough time. Depleted soil levels can also invite rainwater and melted snow deeper underground, thus, increasing the likelihood that water will encroach upon your crawl space, basement, and foundation. Water entering any of these areas can lead to cracks, rotted wood, leaks, and potential floods.

Repeated swelling and shrinking of sandy clay soil particles can also cause similar problems in your home. Aside from causing concrete to crack or sink or water damage to your home space, swell-shrink cycles of sandy clay soil can also result in 2 common phenomena known as the Clay Bowl Effect and Hydrostatic Pressure. Both phenomena are caused by weakened soil that allows water to accumulate in large volumes around homeowner’s crawl spaces, basements, and foundations. Although drastic damage takes a significant amount of time to form from either the Clay Bowl Effect or Hydrostatic Pressure, you still want to be protected as soon as possible to prevent major problems. 

In order for your house to be built, contractors must excavate the earth to form a hole in which they can work. After completion of your home’s foundation and basement, this hole is refilled with surrounding soils. However, this soil is a lot weaker than the denser, untouched soil and, as a result, absorbs water much more readily, forming a “clay bowl” of water directly surrounding your house. The Clay Bowl Effect can actually pave the way for hydrostatic pressure, or pressure by large quantities of water upon your home structures. Hydrostatic pressure is quite common around basement and foundation walls, where it causes them to buckle or bow inwards.

The red clay soil that is found through much of Northeast NC is iconic. It is rich, fertile, and has many strengths. Unfortunately, it can also present a number of challenges to homes and structures that are built on it, especially during the stormier seasons of the year. This is because clay soils are expansive and water reactive in nature, and can become quite unstable when they are extremely saturated or dehydrated. Of course, many parts of Northeast NC also have the state soil (Cecil soil) that is far less reactive, but also has some limitations and weaknesses.

In fact, almost all soil has some weaknesses to consider. This is why contractors often seek to build in areas that have balanced, mixed soil. While expansive soils can be strong, you see, they are changeable. Keeping them stable requires careful and consistent moisture management around a home. If the soil becomes very saturated, it will swell and become soft and marshy. This can lead to subsidence and even heaving in concrete surfaces and structures.

If the soil becomes very dehydrated, however, it will shrink and become brittle. While prolonged droughts are rare in Northeast NC, they can happen. When they do, the soil can recede and crack quite dramatically. This leads to an issue known as settlement, whereby a foundation fragments and sections of it fall into the voids left in the earth. This destabilizes a property, and when the drought breaks, it will let water seep into your home.

Soil bows to the whims of nature. Our area has seen many wild weather events, including thunderstorms, tornadoes, and earthquakes. All of these can impact your home and patio by affecting the soil. 

Flooding 

Soil suffers greatly from water, but especially from flooding events. Flooding causes soil to swell with water and loosen, allowing it to erode over time. Given enough time, this will hollow out a cavity beneath the concrete slab. 

Alternatively, flooding can soften the soil to the point where the weight of the slab forces the muddy earth to ooze out from beneath it. Waterlogged soil can even cause the slab to sink. 

Water can apply more force to the earth supporting your patio than many realize! 

Thawing 

As the soil freezes and thaws over the seasons and many years, small shifts in the soil can also develop and cause sinking. This is a weathering process where the soil passes through cycles of shrinking as it dries and expanding as it freezes. 

Waterlogged soil will see a much more rapidly developed impact of freezing and thawing, as there is more moisture that will develop ice crystals. These crystals are what push the soil particles apart. 

Pests and Animals 

Burrowing pests that excavate soil will cause weak points in the compact soil under the patio. Animals that aren’t burrowers themselves may still seek out cavities beneath the slab as a den, and in doing so may cause further damage to the earth. 

The creation of burrows also creates a pocket of air just waiting to collect water during flooding. Even without water further softening the soil, a network of burrows can weaken the integrity of the soil, eventually leading to a sinking or cracked patio. 

You can read more about animals that can damage your home!